Plow mining method and apparatus



SePt- 21, 1954 F. BAINBRIDGE 2,689,717

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PLOW MINING METHOD AND APPARATUS 9 Sheets-Sheet 8 F. BAINBRIDGE PLOW MINING METHOD AND APPARATUS sept. 21, 1954 A 9 Sheets-Sheet 9 Filed Feb. l0, 1949 Patented Sept. 21, 1954 2,689,717 PLOW MINING METHOD AND APPARATUS Featherstone Bainbridge, Fenliam, Newcastle-on- Tyne, England,

assigner to Huwood Mining Machinery Limited, `Gratesheal-on-Tyne, England, a company of Great Britain Application February 10, 1949, Serial No. 75,699

Claims priority, application Great Britain 1 Claim. l

This invention comprises improvements in and relating to the mining or winning of coal or other material, and is concerned with that method of operation (hereinafter termed method of the kind described), in which the material is obtained by slicing or stripping it from a face by means of a device, herein for convenience termed a plough, which is traversed under power along the face and is provided with a Wedge formation and a cutting edge to cut and lever away the material.

This method has heretofore been used in coal mining but the present invention is not restricted to the Winning of coal but may be applied to the treatment of mine or like faces of other materials. l

Heretofore, the plough has been constructed to slide over the floor and to direct coal on to a cham-scraper conveyor laid along the face and it has been kept up to the coal face by running it along the floor in contact with the conveyor structure which has been made appropriately heavy or massive for the purpose. It has been hauled along the face by a rope haulage and has been provided with ramp or scoop means which, as the plough was hauled along stripping the face, directed the cut down coal on to the conveyor.

The method referred to above as heretofore applied to coal mining, requires no undercutting of the coal, and no shot ring to break down the coal, and the loading of the coal on to the conveyor has been effected by the plugh`concurrently with the cutting. It is therefore Ya simple method and in appropriate circumstances has obvious advantages from the economical and practical standpoints.

The method has been used with success in the mining of soft coal which can be relatively easily sliced or stripped from the face. In the case of comparatively hard coal, however, difficulties arise in getting the plough to slice the coal owing to the resistance which the coal offers to cutting by the plough due to its hardness. Another disadvantage is that it has usually been necessary to cut out stalls at the ends of the coal face to enable the plough to be given a start because it has been required to be held up to the face by the conveyor structure which has only extended to the ends of the face. Moreover, when cutting is finished, the conveyor must be moved to a new position and in the ordinary way the advancing of conveyors in coal mines is a relatively long and tedious procedure.

An object of the invention is to provide improved method and apparatus whereby the above difliculties can be overcome and mining by a method of the kind described, carried out thereby substantially without departing from conventional practice in the lay-out of a mine,

According to this invention, a method of the kind described is characterised in that the plough is traversed along the face supported by side structure of a conveyor laid along the face and extended beyond an end of the face into a gate or road and that for the start of a movement along the face, the plough is brought into the gate or road supported by the conveyor side structure and then caused to start its operation by cutting a kerf, for entry of the thin end of the wedge-formation of the plough, round the corner of the said end of the face, after which the plough is caused to continue cutting of a kerf for entry Y of such wedge-formation as the plough proceeds along the face supported by the side structure of the conveyor.

According to another aspect of this invention, a method of the kind described is characterised in that the plough is mounted to travel along the face supported by side structure of a conveyor into which the plough delivers material won from the face, and the conveyor structure is extended beyond the ends of the face into gates or roads and in the latter is supported on portable struc- =tures made capable of ready movement along the gates or roads. p

The plough is suitably kept up to the face at the start of and during the run along the face by preventing it from rising from the structure by which it is supported and by preventing it from partaking of lateral movement with respect lto that structure. A

Another` feature of the invention consists in bringing the plough, supported by the conveyor side structure, into one of a pair of gates or roads on reaching the end of the face at the termination of a slicing or stripping operation on the face, and then moving the plough and end parts of the conveyor structure along the gates or roads to advance to a new position while at the same time advancing the conveyor structure between such end parts by means operating on the structure at spaced points along its length. Y

Apparatus according to the invention comprises a conveyor tted With side members forming supports for the plough in its movement along the face, such conveyor structure extending at an end thereof into a gate or road at an end of the face so that the plough may substantially Wholly enter such gate or road supported by said side members, and cutting means provided at the thin end of the Wedge formation of the plough and operative continuously to cut a kerf in the material for entry of the wedge formation.

The plough and the said side members are constructed to have such engagement with each other that, at the start of and during the operation of slicing or stripping the face, the plough is prevented from rising from the conveyor structure and from partaking of lateral movement with respect to that structure.

For the purpose of advancing the conveyor structure after a stripping operation on the face, portable structures made capable of ready movement along gates or roads are provided to support end parts of the conveyor structure in such gates or roads. The part of the conveyor structure between these end parts can be moved forward at the same time by means of jacks or sylvesters disposed at spaced points along that part of the conveyor structure.

The winning operation is materially assisted by the fact that the invention provides for the formation of a kerf continuously in advance of the thin end of the plough wedge-formation in combination with the mounting of the plough on the Conveyor structure and the extension of the latter at the ends into gates or roads thus supporting the plough conveniently for starting and continuing the formation of such kerf. Hard coal faces can be efciently dealt with because all the time the plough is moving, including at the start, the continual formation of the kerf facilitates the cutting operation required of the plough and enables the thin end of the wedgeformation easily to enter the material for levering it away. Naturally, the improvements of the invention can be applied to the winning of soft coal or other like materials from faces, and when a cut is finished simple operations sufce to move the whole structure, including the plough, up to a new position, and the lay-out of a mine comprising face and end gates or roads may be according to normal practice, and no formation of stalls is required. The moving up operation is readily effected, for although the conveyor structure is suitably made of heavy calibre for the running thereon of the plough, that part of it lying along the face can be moved up by the jacks or sylvesters disposed at the spaced points along its length, vwhile the portable structures in the gates or roads enable the end parts to be dealt with readily even when the plough is supported on them.

In order to enable the invention to be readily understood, reference is directed, by way of ex- 2 ample, tothe accompanying drawings in which:

Figure 1 is a plan of `coal-mine workings installed with apparatus present improvements and operative for carrying out the method of the invention in connection with the mining of coal.

Figure 2 is a view to a larger scale showing part of the coal face, a sectional plan of the plough and a part, in plan, of a conveyor for talring away the coal removed from the face.

Figure 3 is a rear elevation of parts shown in Figure 2.

Figure 4 is a sectional elevation looking on the right-hand end of Figure 2 and the left-hand end of Figure 3, parts being omitted for the sake of clearness.

Figure 5 is a fragmentary view showing details.

Figure 6 is a plan view of the conveyor troughing and associated parts.

Figure 7 is a sectional view showing apparatus of the invention in a main gate or road.

Figure 8 is a sectional plan of Figure '7.

Figure 9 is a view similar to Figure 'I but taken at a tail gate or road.

in accordance with the Figure l0 is a sectional plan of Figure 9.

Figures l1 and 12 are side elevati-ens of parts of a wheeled structure situated in the main gate.

Figure 13 is a fragmentary elevation of the plough, looking on the right-hand of Figure 2, and

Figure 14 embodies an elevation of a modified construction of plough.

In Figure 1, a coal face I is shown in process of being stripped by a so-called plough 2 which is mounted to travel along the conveyor t and is able to attack the coal in either direc-tion of such travel. The conveyor is laid along the face l and extends at both ends into gates or roads Ll, 5. At the ends the conveyor comprises sections, hereinafter referred to, whichY are embodied in portable structures 6, I. The latter are fitted with wheels engaged with tracks Q, so that they may be moved up as the face l advances, as indicated by the arrows. The plough 2 is of broadly known form in that it embodies a structure which has wedge-formations, at Iii, presented in opposite directions, which are operative to attack the coal face I somewhat like the edge end of a chisel. As will be understood, one wedgeformation of the plough 2 is eiective in one direction of travel of the plough along the coal face I .and the other is effective when the movement of the plough is in the opposite direction. The coal removed by the plough is loaded thereby after usual manner on to the conveyor 3 which is shown of chain-scraper type though, alternatively, a trough conveyor with belt could be used, laid along the face parallel thereto.

As shown by Figures 2 to 4, the plough coinprises a main body or carriage Ii of bridge-like form lying astride the conveyor troughing, and carrying at one side a part I2, hereinafter for convenience termed the wedge part, having the wedge-formations Ill. rhis wedge part I2 overhangs the inner side of the troughing and extends practically to the level of the floor I3 the face I while rising substantially the height of the seam. The wedge-formations Iii are defined by renewable wedging blades It which extend curvedly ,at an incline from the thin ends of the wedge towards the main body Il, see Figure 2. Between the wedging blades ItV and end parts I5 of the main body II which slope down to floor level and serve to, clean the floor of remnants of broken down coal, the plough has inclined ramps or scoops Iii which guide the mainV broken-down coal into the conveyor troughing.

The plough is mounted to travel along the conveyor troughing on 'four vertical wheels I1 and is prevented from slewing horizontally by four horizontal wheels I8 which take bearing on opposite sidees of the troughing. The conveyor is madeof relatively heavy construction. As shown in Figures e and 5 the side members of its troughing are suitably of Y section built up from Z-section parts I9 placed back to back and secured by bolts 20 to the bottom 2l of the troughing. The bottom 2| is thus elevated to provide space beneath for the return flight of the conveyor Scrapers 22, andrso that the chains 23 of these Scrapers may bear on the inner anges of the lower Z-section parts I9. Arranged on the outer sides of the troughing I9, 2i are channel section members 24. These latter have spaced along their length and welded thereto, pairs of lugs 25 which are spigoted to engage holes in such members, Figure 5. These lugs engage over Figures 5` the outer flanges of the side members I9 of the conveyor troughing, Figures 2, 4, 5 and 6, and are secured thereto .by removable pins 26 passed through holes in the parts 25, I9. It will be realised that the construction of the conveyor and members 24 is such that the parts may be dismantled easily to get at the lower scrapers and chains of the conveyor, should that be nec-4 essary at any time. Between the flanges of the members 2li, the running wheels II of the plough are entered. These wheels are slightly coned to fit between the ilanges and there is a pair at each end of the plough carried by parts of, or brackets on, the main body I I which depend over or overhang the conveyor 3 on the outside. They are carried on horizontal spindles running in suitable bearings and it will be apparent that the upper flanges of the members 22 will prevent the plough 2 from rising on either side and that the plough will not tip over away from the coal face I but will be kept up to its work. The horizontal wheels i8 of the plough are carried by lower parts of the main body I I and bear on the outside of the web of the members 22. It will be realised that these wheels, which in plan are situated at the corners of a truncated isosceles triangle Whose apex is on the face side'of the conveyor 3, provide a desirable support or restraint for the plough against lateral movement, so that it cannot slew horizontally. Altogether, therefore, the wedge part I2 of the plough is kept substantially true with respect to the face and as will be understood this makes for very eficient initiation of the operation of the plough and its continuance satisfactorily in slicing or stripping the face I.

For cutting a kerf 21, Figure 2, ahead of the thin end of the wedge formations Il) of the plough, a vertical series of picks or cutters 28,

wedge part I2 of the plough. These picks 28 are adapted to move in a circular path and for this purpose the sets of picks are mounted on carrier 29 which is a sort of H-shaped structure and has the picks disposed down the sides of the' H on the outside edge, see Figure 3. 'I'his carrier 29 is holed at two places (as at 39, Figure 2), on the cross-bar part of the H and spans across the outer ends of the two wedging blades I4 of the wedge formations I il of the plough 2. It may contact slidably with surfaces 3| parallel with the coal face, see Figures 2 and '3. @de holes 30 of the carrier 2e are fitted with bearing bushes 32 by which the structure is mounted on roller bearings 33 on a pair of eccentrics 3l! carried on roller-bearings 35 on short horizontal fixed spindles 36. Only one of the eccentrics and associated parts is shown in Figure 2 but it is believed that this will be suincient for a proper understanding thereof. As will be seen from Figure 2, the cross-bar of the H-shaped carrier 29 is set back from the plane of the sides of the H to accommodate it in the outer compartment 3l', of a doubly compartmented gear box which is supported onor embodied in the wedge part I2 of the plough and extends along between the wedging blades Ill. The spindles 35 are mounted in the` Walls of this gear box and concentric hub parts 38 of the eccentrics 3d thereon carry gear wheels 39, see also Figure 3. These mesh with a central gear wheel i0 that is driven by a pinion lil on a drive shaft (not shown) which extends into the inner com* partment 22 of the aforesaid gear box and carries therein a gear wheel 43. The latter is meshed 3 and 4, is provided at each end of the these ends of the blades I4, which are chamfered to provide flat comprises the motors with gear wheels 44 mounted on the shafts of a pair of hydraulic or other motors 45 which extend over the conveyor 3 and form part of the main bridge-like structure I I of the plough `2. y

It will now be apparent that under the action of the drive from the motors 45, the eccentrics 34 will cause the picks 28 to have quickly repeated movement arising from the motion of the carrier 29- which will receive forward and backward movements with intervening upward and downward movement from the eccentrics. The sets of picks will suitably be withdrawn to the outer edge of the wedging blades I 4 on the retractive or backward movement. and be projected forward with a rotary motion from that edge to effect a cutting action on movement component. Thus, each set of picks forms a vertical kerf in advance of the adjacent wedging blade Ill, the kerf being constantly maintained and formed so that, after each fresh cut when the picks are retracted, the outer end of the corresponding wedging blade I 4 can nose itself into the kerf and exert leverage to break away the coal. Of course, it is only the forward set of picks 28 which is effective at any one time.

On traverse of the plough in one direction one set of picks is operative, while in the opposite direction of traverse, the other set is effective for kerf cutting. Thus, in Figure 2, the set of picks on the left is operative to cut the kerf 21, the plough being traversed in the direction shown by the arrow. In Figure 3 the same set of picks appears retracted. The depth of the layer of coal'removed by the plough may usefully be 12 inches in hard coal, though obviously the depth may be varied according to circumstances. If desired, the sets of picks 28 could be arranged on vertical rods or bars mounted at their ends on revoluble crank discs or devices. Moreover, instead of using the sets of picks for making the kerf, cutter chains or circular sawsfcould be used, though the pick arrangement described, which in its operation simulates a miners pick action, is to he preferred.

Any suitable power means may be adopted for effecting travel of the plough along the conveyor troughing, and in the drawing haulage by an endless rope 46 is shown and will be hereinafter described.

The conveyor troughing form after normal mining understood from the portion thereof depicted in Figure (i. The tracks 2t, for the plough wheels Il', i8 are also sectional as shown in Figure At the ljoints between the troughing and track sections I9, 2i! cross-members le may be laid on the floor for supporting purposes. From the illustration shown in Figures 7 to 12 it will be seen that the end sections, at d1 and 48, of the conveyor troughing and plough tracks extend into the main and tail gates li, 5 respectively and are supported there by the wheeled structures 6 and 'i aforesaid. The latter support or comprise drive and return heads of the conveyor and the conveyor chains 23 (or belt if used), are looped here to movev on their returnjourney. The wheeled structure 5 (Figures 7 and `8) comprises two parts, shown also in side elevation respectively in Figures ll and 12, which are joined by the end section 4l of the conveyor-troughing and plough tracks. The one of such parts, that shown in Figure 1l, embodies the drive head for the conveyor while the other (shown in Figure 12), comprises a haulage drive. `The drive head 4S which operate through duid couplings 5t, reduction gear boxes I and I9, 2l` is of sectional the downward practice as will be,

sprocket and* chain gear .52 to rotate the drive sprockets 53 of the conveyor chains 23. The haulage drive comprises a drum 54 (about which the endless haulage rope l5 has two or three turns), and a motor 55 which vdrives the drum 54 through V-belt gearing 5e and a gear box 51. The haulage rope passes to and from the drum ft over idlers 58 and runs along the top of the conveyor troughing to the Wheeled structure 'l in the tail gate 5. In the main gate 4 the wheeled structure e spans a gate conveyor 59 on to which coal is shot from the face conveyor down a chute 66 supported on the conveyor drive head. At the wheeled structure 1 in the tail gate 5, the rope te passes over the vertical grooved pulleys iii, Figures 9 and 10, and then moves in a loop over the horizontal grooved pulley 6,2. The tension on the rope is adjustable here by adjustment of the frame B3 containing the pulley 62 and there is also a screw adjustment 6e for the return sprockets 65 of the conveyor chains 23. The structure 1 thus embodies what is generally termed a tension head for the conveyor 3. Means, not shown, may be embodied in the undercarriage parts of the wheeled structures e and 'i for adjusting the height of the undercarriage chassis on its Wheels in order to accommodate slight variations in the depth of the door of the gates d and 5 With respect vto the floor i3 alongthe face l.

The Wheeled structures 6 and 'i can readily be moved along the gates on the tracks 8, S by means 'of such devices as rotary sylvesters and hauling ropes (not shown). They can thus be relatively easily moved up as the face l is advanced. At spaced points along the face conveyor, for eX- ample at positions such as are indicated in Figure 1 by the dot-and-dash lines 66, men with 'sylvesters or jacks at the same time operate on the intermediate part of the conveyor 3 to move that up as Well. The whole operation can be performed in a very short time and With much economy of labour as will be understood. The gates are of normal construction and at the end of arun the plough is brought on to the wheeled structure in one of them to be moved up on that structure. Y

In order to connect the plough to the endless haulage rope l5, use is suitably made of the clamp device shown in Figures 2, 3 and 13. This device comprises two tongs-like Vparts 5l, 58, of which the part 6l is of box-like form mounted across one end of the plough 2. The other part ed, of iJ-section, is pivotally mounted within the part at 5e. The parts Sl, @shave respective grip jaws l5, 'il fitted with slippers 'i2 to grip the rope et on the flight thereof nearest the coal face I. A heavy grip is necessary to take the strain put the plough in slicing the face and for this reason the clamp parts 5l, 58 are of relatively heavy construction and operated by a hydraulic jack 'le which in turn is operated by an oscillatable hand lever lt. The clamp device is disposed at the rear end of the plough and its position can be changed to the other end thereof according to whether the installation is operating on left-hand or on a right-hand, coal face. The rope 4E is passed through ahole 'l5 at one end or the other ofthe plough structure so as to be heneath and avoid obstruction of the scoops or ramps I5 up which the coal passes to the conveyor 3.

In the opera-tion of the apparatus described, the plough may at the start of a face operation be on the wheeled structure 'l in the tail gate Il, its position being indicated by the dot-and-dash 8` lines at A in YFigure 10. The conveyor 3 would have been moved up or laid along the face and it would be disposed so that the picks 28 at the operative end of the plough are round the corner, at c, of the adjacentY end of the face as indicated at the position A. The depth to which the picks are around the corner of the coal face, corresponds to the depth of the layer of coal to be stripped from the face as will be understood. The haulage rope 46 having now been put into operation, the motors 45 of the plough picks 28 are started and the clamp device 6l, S8 closed on to the haulage rope. The plough now starts its journey along the face and the full line showing thereof in Figure l0 indicates that the plough has gone just a short distance, a slightly longer distance having been covered in the diagrammatic Figure l. At the outset, the said picks 28 nrst start to cut a kerf for the entry of the corresponding wedge formation lil and thereafter the kerf cutting is continued, as at 21, Figures 2 and i0, for continued entry of the wedge formation and breaking away of the coal. Eroken down coal falls in front of the plough and as indicated in Figure l0, and similarly in Figure l, moves up the corresponding ramp or scoop it of the plough into the conveyor troughing i9, 2l. ln this it moved along by the Scrapers 22 (or belt) to the chute to, at the head end of the conveyor 3, and from there is deposited on to the main-gate conveyor 59, Figures i and 8. As the plough travels along, its weight and lateral forces thereon are exerted through the wheels Il, le, on the channel members 2E which are secured by the lugs 25 and pins 26 to the outer ilanges of the members i9 forming the sides of the conveyor troughing. The said flanges, through the lugs and pins, support the plough tracks 2d and though the outer track members may, as shown in Figures 4 and 5, bear on the floor cross-members 1S disposed at the joints in the side members of the conveyortroughing, the bulk of the weight, and the lateral stresses, on the plough are taken by the conveyor troughing as will be understood. The plough track members 2d lend weight to the conveyor structure, which is already of relatively heavy construction as aforesaid, and thus assist it in keeping the plough up to the coal face. When the plough 2 completes its cut (dot-and-dash line position a. in Figures 7- and 8), the clamp device Si', 68 is released.` and the haulage motor 55 stopped. The plough is novvon the wheeled structure 5 in the mother gate and situated substantially wholly in that gate. By operation of the rotary sylvesters and of the sylvesters or jacks at 5e, both aforesaid, the wheeled structures 'l and the conveyor 3 are noW advanced to take up position for a return out onV the coal face, as indicated by the dot-and-dash lines at b in Figure 8.

Similar kerf cutting and breaking down of thev coal to those vabove described, but by operation of the other set of picks 28 and the corresponding wedge formation Il) are now effected during traverse of the plough 2 along the face to the tail gate 5. For this operation, the direction of movement of the haulage rope 45 is reversed. .As the plough travels along, the broken down coal moves up the other scoop or ramp i6 on to the conveyor 3 and it is taken away by the conveyor through the arch formed by the bridge-like main structure Il of the plough. When the plough reaches the wheeled structure in the gate 5, it will have the position indicated at B in Figure 10. rlhe clamp device 51, 68 is now released, and the haulage motor 55 stopped, whereupon the parts are again advanced for a fresh operation on the coal face in the opposite direction. The initial position of the plough for this operation is as shown by the dot-and-dash line at C in Figure 10.

Further operation will lbe understood without more description.

It will be apparent that the bridge-like main body l l of the plough 2 as illustrated by Figure 4, extends from side to side over the conveyor at a good height. This form of the plough is intended for use on a normal coal seam, say 3 6" (about 1 metre) high which is relatively high compared with some seams. At the height stated the bridging part of the plough is suliciently high above the conveyor 3 to enable the cut coal, brought into the conveyor troughing by plough ramp or scoop Iii, to pass beneath the bridge 4to delivery from the conveyor at the main gate 4, whenl the plough is operating during travel from the main gate 4 to the tail gate 5. Thus, the plough can be operative in both directions of traverse thereof along the face. In one direction, of course, i. e. with the plough moving unidirectionally with the conveyor scrapers or belt, the coal does not need to pass the bridge but when stripping the face by moving the plough in the opposite direction the coal scooped on to the conveyor must pass the plough and it does so through the bridge-form main body or carriage I I.

In a modified example for use with low seams, the conveyor construction and the mounting of the plough 2 on the conveyor may be similar to those abovedescriebd, as shown in Figure 14. The bridge-form main body or carriage Il of the plough, however, is of flatter construction with the motors 45 for driving the kerf cutting picks 28 in a lower position. In this example, the bridge cannot be high enough for the coal to pass through it and therefore the plough is made operative to strip coal from the face in one direction of traverse only of the plough along the face, being ilitted back to the starting point for a fresh cut. If desired, therefore, a form of plough may be used which comprises only a single wedgeformation and set of picks 28 for stripping the face l and a single ramp or scoop I6 for directing the coal on to the conveyor 3. Nevertheless, similar principles of operation are involved to those in the case first described though appropriate modication of the driving means between the motors 45 and the picks 28 would be necessary, as will be understood.

According toa further modification and in order to provide for operations of the plough in higher seams, the carrier 29 of the picks 28 may be extended upwardly as shown by way of example by the dot-and-dash lines at |00 in Figure l 3. This provision can be carried out by tting additional pick-carrying parts to the carrier or by making the side parts of the H-shaped carrier structure detachable and replacing them by pickcarrying parts but of extended height. Similarly, for lower seam ploughs (cf. Figure 14), detachable pick parts of this nature may be fitted.

It is an advantage of the invention that the plough can be adapted to cut practically the full height of the seam because it provides for a clear out of the face from top to bottom. 'I'he invention employs certain features of the inventions forming subject-matters of my concurrent patent applications Serial Nos. 75,697 and 75,698, but no claim is made herein to these features per se. Obviously, the apparatus described may be provided with features, other than those already referred to, to be found described in the 10 specications accompanying such patent applications.

I claim:

Apparatus for stripping material from a face underground, comprising a plough and a conveyor on which said plough is supported during movement thereof along said face, said conveyor being laid along in front of said face and extending at each end thereof into a gate or road at the adjacent end of said face so that the plough may substantially wholly enter the respective gate or road supported by said conveyor, and said plough having a wedge formation at each end so as to be operative on the face in each direction of travel of the plough along the face and the thinner end of each wedge formation lying substantially parallel to said face in the top to bottom direction thereof, said plough and conveyor being engaged with each other on both sides of the Vconveyor by means operative substantially rigidly to prevent the plough from rising from both said sides of and from slewing laterally with respect to said conveyor, said plough also comprising a series of tools located adjacent and substantially parallel to the tip of said. thinner end of each wedge formation, and which are movable back and forth intermittently by quickly repeated movements and operative to pick at said material at numerous points disposed relatively closely together in an approximately straight line to form a kerf of substantially even depth ahead of said tip starting round the corner of said end of said face and of such nature as to be substantially wholly parallel to said face in longitudinal and transverse section, each Wedge formation and the respective series of picking tools being so relatively disposed that the thinner end of the wedge formation enters the kerf when the latter is only of shallow depth and this relation between them is maintained throughout the travel of the plough along said face, the conveyor being operative constantly in one direction of travel and the plough being constructed to bridge the conveyor transversely at a high elevation above it suflicient for large lumps of the material fed onto the conveyor by the plough to pass beneath the bridge, and the conveyor at each end being free of the upstanding wall onthe far side of the gate or road at each `end` of the face.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 294,247 McDonald Feb. 26, 1884 1,201,537 Wissemann Oct. 17, 1916 1,522,693 Morgan Jan. 13, 1925 1,563,153 Brackett et al Nov. 24, 1925 1,710,801 Morgan Apr. 30, 1929 1,711,280 Morgan Apr. 30, 1929 1,735,583 `Morgan Nov. 12, 1929 2,425,108 Mavor Aug. 5, 1947 FOREIGN PATENTS Number Country Date 578,832 Germany June 19, 1933 590,604 Great Britain July 23, 1947 642,686 Germany Mar. 12, 1937 896,299 France Apr. 24, 1944 OTHER REFERENCES Information Circular, Design and Operation of the Coal Planer, Ruhr District, Germany, U. S. Dept. of the Interior, Bureau of Mines, October 1946 by John W. Buch (5 sh., Figs. 13a, 15, 16, 17 and 20, and page 9). 

